The ultimate goal is the divine functional, a exchange correlation functional that perfectly describes many-body and quantum effects. There are numerous ways at how to do this. Jacob’s ladder starts with the simplest inclusions and ends with the most complex inclusions. Jacob’s ladder is:

LDA: only local electron density
GGA: LDA with gradient correction
Hybrid: GGA with exact exchange term
Meta-GGA: GGA with improved gradient correction (+ kinetic energy density)

Note that this ladder, in going down, also increases in computational cost, with LDA being the least costly.